This design allows the block to be secured onto vertical 2040 aluminium extrusion instead of the horizontal 2020 aluminium extrusion

I am using this filament guide (https://www.thingiverse.com/thing:3015832) currently. So you can use them without modification.

Parts list:
1 x Z axis guide
1 x ID 8mm OD 22mm (608) bearing
4 x M3 12mm
2 x M3 washers to hold the bearing
2 x M3 nuts
2 x M3 T nuts